Carbon-ball transmitter.



No. 844,635. PATENTED FEB. 19, 1907. K. M. TURNER & N. W. JOHNSTON.

CARBON BALL TRANSMITTER Jam; o JAH #ilk-74W# TE STATES PATET OFFIOE.

KELLEY M. TURNER, OF NEW YORK, AND NORTON W. JOHNSTON, OF CHAP- PAQUA,NEW YORK, ASSIGNORS, BY MESNE ASSIGNMENTS, TO GEN- ERAL ACOUSTICCOMPANY, A CORPORATION OF NEW YORK.

CARBON-BALL TRANSNHTTE.

Specification of Letters Patent.

Patented Feb. 19` 1907.

Original application filed September l8, 1905, Serial No. 277,61 6.Divided and this application filed September 8, 1905- Serial No.277,615.

To 11,27/ whom, it may concern.: Be it known that we, KELLEY M. TURNERand NORTON W. JOHNSTON, citizens of the United States, residing,respectively, at the city of New York, county of New Ork, and State ofNew York, and at Chappaqua, county of Westchester, and State of NewYork, have invented certain new and useful Improvements in Carbon-BallTransmitters, io of which the following is a full, clear, and exactdescription.

Our invention relates to carbon-ball transmitters. In our companionapplication, Serial No. i5 277,616, filed herewith, we have particularlydescribed the features of a transmitter which is adapted to containcarbon balls as the operative element. In the present divisional case.we desire to particularly describe and zo claim the construction andarrangement of the carbon-ball element per se.

Carbon balls have hitherto been used in telephone-transmitters; but sofar as we are aware their use has been entirely abandoned in all modernpractical telephone-work. The reason for this abandonment was on accountof the inertia of the carbon masses, which were constrained to takehigher rates of vibration than it was possible for them to at- 3o tainunder the influence of a transmitter-diaphragm. W hen balls of anyordinary size, such as have always been employed, were used, thevibrations of the diaphragm caused the balls to be knocked back andforth en- 3 5 tirely out of rhythm with the diaphragm, so

that the electrical pulsations instead of corresponding with the soundare largely the result of the impact of the heavy balls against thediaphragm in their independent move- 4o ment. In other Words, as thediaphragm vibrates the heavy balls acquire suoli an inertia that theywholly break contact therewith and in returning to position strike thediaphragmsurface with such a hard blow as to produce too great a contactand obviously one having no relation to the sound transmitted. Thisdefect is known as cracking or frying and is quite intolerable inpractice. In order to overcome the defect, suoli balls have 5o beenabandoned and pulverized oi granulated carbon substituted therefor,which is free from the above defect, although it is not pack hard and isnot very sensitive. The

production of an exceedingly sensitive transniitter is a greatdesideratum in the tolephone art,-particularly for long-distance work.Such a transmitter would also be advantageous in local work, since itwould 'avoid the necessity of placing the lips closely 6o thereto, whichis obnoxious from a sanitary standpoint. By the present invention weprovide such a transmitter.

Our invention consists in the construction, combination, location, andarrangement of parts, all as will be more fully hereinafter set forth,as shown in the accompanying drawings, and finally particularly pointedout in the appended claims.

The drawing shows a 0'ready-enlarged sec- 7o tional view of a carbonalltransmitter embodying the principles of our invention.

Broadly stated, our invention consists in making and using carbon ballsof exceedinglyreduced'diameter, amounting to three 75 or four times assmall in diameter and from twenty-seven to eighty-one times as small inmass as those heretofore used. The effect of such a marked reduction inthe size of the balls is manifold and leads to the most sur- 8o prisine'results in practice. By virtue of the exceedingly-reduced inertia eachball can attain a proportionately higher rate of vibration and inpractice a vbration which accords with any ordinary tone of speech usedin telephone transmission. Also by virtue of the reduced inertia thereis no hammer effect of the balls against the diaphravm when returningthereagainst to produce the objectionable frying and cracking el'l'ecthereto- 9o fore always incident to the use of balls. By virtue of thereduced size the number of points of contact is increased as the cube ofthe diameter, with a proportionate increase in sensitiveness ande'l'liciency. At. the same 95 time there is retained all thc advantaweswhich are obviously attendant to looseymounted balls-namely, extrememobility and uniform contact through out the mass which the balls makeon account of their roo symmetrical contour.

Referring to the drawing, which is drawn to a greatly-enlarged scale inordcr that the sha ie of the individual balls may be possible ofillustration in somewhat near the proper an advantageous material, sinceit is apt to 1 relative size thereof, 1 designates a carbon block havingrecesses 2 in the face thereof, which we preferably form ofhemispherical section, and polished interiorly in order to obtain moreefficient contact and to enable greater mobility of the balls. Aconvenient arrangement is to make the block 1 circular and to. arrangethe recesses 2 annularly around the face with an additional cavity3 atthe center.

4 indicates a base-plate into which the block l is inset as described inour, companion applicationF above referred to.

5 designates the carbon diaphragm, which is supported in exceedinglyintimate roximity to, but not actually touching, the lock 1, as also setforth in the above case.. The arrangement is such that the diaphragm 5does not vibrate sufficiently vto quite touch thee block 1 under anyordinary vibrations incident to its use in telephone-work.

Within the recesses 2 We place the carbon balls 6, so as tosubstantially two-thirds fill each cavity formed between such recessesand the diaphragm 5. `The size of these balls approximate thecharacteristics of very fine sand, they being, in fact, from twotenthsto five-tenths of'a millimeter in diameter.

among themselves with every vibration oi the dia hragm. They do not packtogether in use, ut retain their mobility and secure a multitude ofcontact-points, and have masses whose inertia is so small as toaccommodate any periodicity of diaphragm vibration.

Wcv do not, of course, desire to be restricted to the exact size of theballs which These balls lie loosely in their containing-recesses and-move about freelyl aliases we employ, it being merely essential to usea size whose inertia is at least ten or twenty times as small as theforms heretofore used, it being evident that every size of ball has itsown periodicity'ol vibration, and it is merely necessary to go beyondthe limits of vibration of ordinary speech. The transmitter will workeiciently and avoid frying, cracking, and snapping for any size smallerthan the above limit.

What we claim is- 1. In a telephonie transmitter, a block havingcavities, a carbon diaphragm in intimate juxtaposition thereto, andcarbon balls contained between said dia hragin' and said block andloosely collected 1n said cavities, said balls having a maximum diameterof iive-tenths of a millimeter, whereby their natural period ofvibration is greater than the period of vibration of ordinary humanspeech.

2. In a telephonie transmitter, a block having a series of hemisphericalcavities polished on their interior faces, each cavity beingsubstantially two-thirds filled with carbon balls loosely restingagainst the diaphragm, each carbon ball being of a diam- ',eter of fromsubstantially two-tenths to fivetenths of a millimeter, whereby theballs may take a periodicity of vibration which accords with that of thediaphragm.

In witness whereof we subscribe oursignatures'in the resence of twoWitnesses. ELLEY M. TURNER.

NORTON W. JOHNSTON.

Witnesses:

ALFRED W..PRocroR, FRANK S. OBER.

